1. Field of the Invention
The present invention relates to a filter fan.
2. Description of the Related Art
Filter fans are known is practice. The filter means, in particular a nonwoven mat, is held in a frame which is closed to the outside by a covering grid and to the blast by a protective grid, whereby the nonwoven mat is held between both grids and adheres to both grids. The filter fans are used for example in switch cupboards and in other casings, namely in a cut-out of the respective casing wall in order to cool electrical or electronic components placed in the casing. This being, it is provided to keep the dust charge as low as possible in order not to reduce unintentionally the cooling power by a dust layer which is depositing on the electrical components. Moreover, the blasts have usually comparably low performances so that the pressure drop at the filter insert is to be held as low as possible in order not to reduce unadmittedly the cooling power due to the filter agent itself. Finally, a protection against moisture is provided against jet water, in particular for devices for example for telecommunication which are placed in halls of companies but which are, for example, placed in the open.
In practice, constructions which have a class of protection IP 54 have proved to be efficient. A higher protection against moisture can be achieved, for example, by filter membranes as they are known from the EP 1 098 692 B1. However, such filter membranes have the disadvantage that they cause a comparably high pressure drop and have in particular a low dust capacity. Moreover, the corresponding filter membranes are laminated which has a disadvantageous economic influence on the fabrication of the filters. In particular, when certain properties are provided for, which either the carrier material or the membrane itself does not have, the respective material must be equipped correspondingly, whereby the equipment eventually of two components of the laminate before the laminating procedure is complicated and eventually makes the laminating procedure more difficult and can thus again have a disadvantageous economical influence.